Casting apparatus



Sept. 28, 1954 w, J, TRETHEWAY ET AL 2,689,989

CASTING APPARATUS 2 Sheets-Sheet 1 Filed Sept. 12, 1951 Sept. 28, 1954 Filed Sept. 12 1951 w. J. TRETHEWAY ET AL 2,689,989

CASTING APPARATUS 2 Sheets-Sheet 2 FIG. 4 FIG. 5

Min,

M 'IIIIIIIIIIIIIIIIIIIIIIIIIIII )wfimwzfiabfiifir)? 120 [2 IyENTORS Fake/my a fgll f'f d' Ker/ward Ear L ,BxI/E'er 6M; 81.31% m. fiwMn 17 ATTORNE s with one form of casting apparatus according to my invention and illustrated in the accompanying drawings, in which:

Fig. 1 is a plan View of the casting apparatus;

Fig. 2 is an elevation in section of the apparatus of Fig. 1;

Fig. 2a is an enlarged sectional view of the thrust bearing of the casting apparatus;

Fig. 3 is a fragmentary view of a portion of the face of one mold half;

Fig. 4 is an enlarged fragmentary View of a smaller portion of the face of a mold half illustrating in more detail one hemispherical cavity therein and the channel leading thereto;

Fig. 5 is an enlarged sectional view on line 55 of Fig. 3;

Fig. 6 is a sectional view on line 66 of Fig.

Figs. 7 and 8 are sectional views on lines 'l'! and 88, respectively, of Fig. 6; and

Fig. 9 is an enlarged cross sectional view of the induction coil of the mold preheating means.

The casting apparatus, as may be seen most clearly in Figs. 1 and 2, comprises a pair of mold halves If; and El supported with their faces opposite one another by cone-shaped supporting members [2 and I3, respectively. The mold halves I0 and H have substantially identical faces as will be more fully pointed out subsequently, the only difference between the two mold halves being that mold half ill has a centrally lo cated circular opening it extending through it. Each mold half is secured to its supporting cone by a plurality of bolts IS.

The supporting cone l2, which supportes mold half I0, is itself secured by bolts it to one end of a hollow shaft ['3 which is, in turn, supported within a combination radial and thrust bearing l8, the outer casing [9 of which is fixedly mounted on a base or pedestal which may be bolted to the floor, or to the bed or crib of the machine. The thrust bearing is comprises the housing It] to the inner face of which are secured two outer bearing races 21 and 22. A second pair of bearing races 23 and 24 are supported on the periphery of the hollow shaft H and secured thereon against relative longitudinal movement and are separated from the bearing races 21 and 22 by two sets of roller bearings 26 and 21, respectively. The faces of the bearing races lie in planes angularly disposed with respect to the longitudinal axis of the hollow shaft ll, as do also the axes of the bearings 26 and 27. An oil hole 28 is formed through the upper wall of the casing l9 whereby lubricating oil may be supplied to the interior of the thrust bearing. It will be clear from the above and from Fig. 2 that the thrust bearing [8 permits rotation of the hollow shaft ll, the supporting cone I2 and mold half It], but prevents any longitudinal movement thereof. Thus mold half it is longitudinally stationary.

The supporting cone l3 which carries the other mold half H is supported by a drive shaft 38 by being secured to one end thereof by bolts 3i which extend through a flange 32 formed on said end of the drive shaft 30. The drive saft 30 is, in turn, supported in a pair of bearings, namely, a forward bearing 33 and a rear bearing 34. The bearings 33 and 34 are of conventional'form and are fixedly supported in any desirable manner upon a crib or bed 35. Each of these bearings is provided with an oil inlet 36 and includes a lubricating oil reservoir 37 through which an oil ring 38 resting on drive shaft 30 is 4- adapted to be rotated by the drive shaft 30, whereby the shaft surface is continually lubricated in the bearings. From the above it will be understood that the drive shaft may be both rotated in bearings 33 and 34 and moved longitudinally therethrough.

At its rear end the drive shaft is provided with a bore 30 into the outer end of which is non-rotatably set a coupling member 4! provided with annular spaced teeth 12. The coupling member 4| and bore ill of the drive shaft 30 receive in a relatively non-rotatable connection a splined shaft 43 connected to the shaft of an electric motor 44 by a coupling 45, the splines of the shaft 43 entering the spaces between the teeth 42 of the coupling member 41. The splined connection, while preventing relative rotation of the drive shaft 30 and the shaft 43, permits longitudinal relative movement therebetween. Thus the motor 44 drives the drive shaft 30 and rotates the mold half 1 I supported by the supporting cone l3. In place of coupling the motor directly to the splined shaft 43 by the coupling 45, as shown, this shaft may be driven by a V-belt drive or by any other desired type of drive.

To provide for longitudinal movement, the drive shaft 30 is provided with a shoulder 59 against which a thrust bearing indicated generally at El is adapted to act to urge the drive shaft 30 to the left, as viewed in Fig. 2, so that the mold half l I will contact the longitudinally stationary mold half l0 face-to-face. An enlarged sectional view of the thrust bearing 5| is shown in Fig. 2a. The thrust bearing 5| comprises an outer ring member 52 supported non-rotatably on the outer ends of a plurality of piston rods 53. A key 54 extends from the lower portion of the periphery of the ring member 52 intov a longitudinal key- Way 55 in a member 55 bolted or otherwise secured to the crib or bed 35. A flanged ring 56 is'bolted to the forward face of the ring member 52, the flange 51 thereof having an inner diameter substantially equal to the outer diameter of the drive shaft '30 and enclosing an oil retaining gasket 58. The ring member 52 of the thrust bearing 5| also surrounds a collar-59 which is secured by one or more set screws 6E1 to the drive shaft 3!]. Between the collar 59 and the shoulder 50 of the drive shaft 38 there are 1ocated a plurality of roller bearings BI supported by spaced annular rings 62 and 63 and flanked on opposite sides by bearing races 6t and 65. A second oil-retaining gasket 63 is provided to surround a portion of collar 59 and is maintained in place by an annular plate 87 secured to the rear face of the ring member 52.

The operation of the thrust bearing 5! to move the shaft 39 ineither longitudinal direction will, it is believed, be clear from the above description thereof but briefly, when the piston rods 53 are urged to the left as seen in Fig. 2, force is conveyed through ring member 52, bearing race 65, bearings BI and bearing race 64 to the shoulder 50 of the drive shaft Bil thereby urging the drive shaft 30 to the left. When piston rods 53 are Withdrawn to the right, the withdrawing force is conveyed through ring member 52 to the flanged ring 56 and thence through the bearing races 64 and 65 and rollers 6! to the collar 59 which is secured to the shaft. To maintain thrust bearing 5| continually well lubricated, an oil hole 66 is provided through ring member 52 for the admission of a lubricating oil.

A hydraulic means 10 is provided to move piston rods 53 and thrust bearing 5| longitudinally age-copes to thereby urge mold hiailf '-ll""into face to-f-aee contact-with mold =ha'1f l or to move -mo'ld half H out of contactand *away'irom mold 'half 10. The hydraulic means "comprises an annular cylinder H connected through a base 1-2 to the -crib or bed 35 of the apparatus. The annular cyh inder I surrounds the "drive s'hai't- 30 but is not in any way in conta'ct therewith. hn-annular piston 7-3 "(Fig 2) is"-c01itained Within "the -an-' nular cylinder "-11 'and-is'connected to "the rear endsofthe connecting rods- 53 which-extend throughthe'forwardwall o'f the'annularcylinder "H. Packing notshown) prevents leakage of fluid from "theannular cylinder H around the piston rods. Hydraulic fluid-is supplied 'to opposite ends of the 'cylinder l l through'supply lines I' l and -15,*the *fluid entering-through the supply line-l5-being'adapted*to urge the piston 13 to the left, as seen in Fig. 2, and the-fluid supplied-through the supplyline 'M-being adapted to urge the piston 13 to the right.

' The structure i of the'annular piston 13 and the piston rings employed in connection with it are'illustrated in more detail-in Figsafi, I -and 8. Theannular piston comprises an annular memher-80 flanked on either side by ring-shaped plates 8| and 82 secured thereto by reason of the reduced .cross sectional area of the inner end-of piston rods 53 which extend through vthe member 80 and-the plates 8l and 82 and are secured thereto by nuts 83. To provide for a close fit *between the piston and the outer wall of cylinder 1|, apair-ofconventional expanding piston rings 84 and 85 are provided :and are located in channels .86 and 81, respectively, formed in theouter surface of the ring'member 80 and partially defined by ring-shaped plates 8| and 82.

To provide *for a close .fit between thepiston and the inner :wall of .theannular .cylinder H, however, a novel type of contracting piston ;ring has been designed. Two such piston rings are illustratedand are locatedin channels 89 formed on the inner face of theuring member 180 and partially defined by the ring-shaped plates Bl and 82.

Each of the oontractingpiston rings 88 comprises a :plurality, :preferably .6 in number, of arcuatelyccurvedangle elements 90,-and a plurality, referably 3"in .:number, of arcuately curved filler segments 9|. The angle segments 98 are arranged in'two side-by-side groups of three :each to form a channel-shaped ring; and the filler segments 9| are laid end-to-end in the channel :defined by the thus assembled angle segments. The outer peripheral edges of the filler segments 9! are. grooved to receive a coil tension spring 92. When the resulting composite ring is .in place against the inner wall of the annular-cylinder 'H,.,narrow spaces 93 exist between the adjacent ends of the segments 98 and 9|. These spaces arestaggered in the composite ring sothat no two of them lie in substantially thesame radial plane. The coil tension spring 92,-which'lies in the peripheral groove formed in the "filler segments 91, urges the segments 90 of thelcomposite ringtowardeach other to form-:an uninterrupted ring and so into tight contact with "theinner wall of the-annular cylinder "H.

In the pistonrings above described, the .filler elements 91 are simply three-in number, each extending substantially one third of the distance about the periphery of the inner wall of the cylinder "ll. Eachof thesesegmentsmay how- 6 ever'be divided into twoby being out-lengthwise. so that in the-assembled ring the filler segments, like the angle segments, are divided into two symmetrical halves-arranged on opposite sides of a plane normal to the axis of the ring. --In such a structure, the coil spring Manet only urges the ring halves against the "inner wall-of .the cylinder ".11, but also urges them tospread apart, into engagement with the.side-walls and the annular ring grooves 89. Of course, in this latter'structure, the iillerelementsand the angle elements may just as well be integral with each other, in which case each ring will consistof 'six segments, three forming the half of the ---ring abutting against that side wall of the channel 89 formed by oneor the other of ='the'-plates" '8l or 82, and the other three forming the half or the ring which abutsagainst the opposite side wall of said channel.

In view of the fact that relatively large forces are-employed in operation of LthB thus far, abovedescribed casting apparatus whereby themold halves l0 and II are urged together under relatively great force, it'isdesirable ancl even necessary to provide means foradditiona'lly supportin the upper end of the thrust-bearing l8 supporting the hollow shaft 11. Such-support is provided by a number of tie rods I fFig. 1')

{adjustably secured between outwardly extending portions 'IOI of the casing [80f thethrust bearing 18 and brackets IMsecuredinanydesirable manner to the crib or-bed35 of the "casting apparatus.

The present casting apparatus, as stated, is adapted to be used in the casting-ofball-shaped cadmium castings. The "faces of-ea'ch-of the molds l0 and II are thus formed withaplurality of hemispherical cavities H 0 (Figs. 3 throug'h fi). These hemispherical cavities I I0 are'arranged in a circle around the outer portions of thcfaces-of each mold half. A plurality-of channels H l' are also formed in eachmold'face, each channel lead-- ing to a hemispherical cavity'and'being adapted to convey molten metal thereto. Inorder that the metal to be cast flows outwardlyinto-the cavities without substantial turbulence and consequent oxidation, the former by itself causing rough-surfaced casting and the latter impure ones, the sides of the'channels l H are tapered to diverge slightly toward the hemispherical cavi ties. This may be seen by reference to Fig.4. Additionally the base of each channel III is provided with a small ridge 1 l2 as maybe seen in Fig.5. The purpose of this ridge is'to decrease the amount of labor involved in separating .the cadmium ball castings from the'sprue which is formed by the excess cadmium employed which hardens or solidifies within a common annular central cavity H4 radially inwardly of channels HI and inwardly of said cavity H4 in the immediately adjacent portion of the mold. This is because the presence of the ridge causes the shrinkage cracks which form upon-solidification of the metal to break 01f the sprue whereby it need not be subsequently brokenoff either manually or mechanically.

Additionally the face ofeachmold'half [B and II is provided with a plurality of spaceddowel pins H3 extending outwardly -therefrom,-:andr;a plurality of holes (not shown) to receive athe dowel pins of the other mold half when'themold halves are in face-to-face contact. The dowel pins servetwo functions; first,rthey properlyposition the moldhalves Hl'and 1H with'respect to one another so that the hemispherical cavities H and the channels III in one coincide with those in the other, and, second, they provide for transferring rotational driving forces from the mold half H to the mold half ID.

The manner in which molten metal is prepared for casting and delivered to the mold of the present casting apparatus is fully described and claimed in our aforementioned application Ser. No. 251,024. A portion of the apparatus employed for this purpose is illustrated in Fig. 2 and comprises an insulated stainless steel delivery pipe H5 provided at its discharge end with a removable gooseneck member H5 at the lower end of which is formed a molten metal delivery spout I l! adapted to discharge molten metal into the composite mold formed by mold halves i0 and l l. A stainless steel bar I I8 is connected to the end of the stainless steel delivery pipe I to supply electric current thereto for the purpose of maintaining the molten metal therein heated to a desired temperature as fully disclosed and described in our aforementioned application. To obtain desirable dense ball castings of cadmium in the present apparatus, the temperature of the mold must be from 400 to 450 F., preferably about 430 F. If it is lower the castings are not smooth but tend to be rough surfaced, whereas if the temperature of the mold is substantially greater, expansion may cause the mold to crack open between the halves, permitting escape of molten metal. As set forth in our aforementioned application, the temperature at which molten cadmium is delivered to the mold of this apparatus should be between 700" and 800 F., and preferably about 760 F.

It will be apparent from the above that in order to start casting with the present apparatus, the composite mold, comprising the mold halves i0 and II, must be preheated to the temperature of about 400-450 F. Two factors are involved in preheating the mold, the first being the length of time required in view of the relatively great weight of the mold and the second being that the parts of the apparatus surrounding the mold, and particularly the thrust bearing i8, must not be overheated. In order to preheat the mold in a reasonable length of time and yet not overheat the surrounding parts of the apparatus, we have designed a novel preheating means. This preheating means (Figs. 1, 2 and 9) comprises an induction coil made up of a number of turns of copper tubing 20 held together at spaced intervals by a plurality of blocks of material H25 in which they are embedded. The composite coil is supported by a plurality of rods 12? which are adapted to extend through openings I23 in a number of the blocks I2 I, the rods 122 being supported at opposite ends by appropriate supports i24 and I25. This supporting means for the coil permits movement of the coil longitudinally of the casting apparatus so that it may be positioned to surround the abutting mold halves l0 and H, as in Fig. 2, or be positioned rightwardly thereof as seen in Fig. 1. Suitable electrical connections (not shown) are provided for the induction coil. In View of the relatively great weight of the mold, relatively high currents must be employed and in order that the tubing of the induction coil and its insulation be not damaged thereby, water or some other coolant may be passed through it. By this heating means the mold can be uniformly heated and brought up to temperature MOW-450 F.) in a relatively short time without overheating of the surrounding parts of the apparatus.

After several casting operations, it will be understood that the mold will tend to become overheated by repeated charges of molten cadmium and thus means is usually provided to cool the mold. This means may comprise an exhaust fan to remove the hot air and smoke from around the motor as well as a fan to provide cool air thereto. In order to maintain and properly control the temperature of the mold, a small thermocouple may be embedded in a brush adapted to continuously engage the periphery of the mold. This thermocouple may be electrically connected to the above-mentioned fans to cause their operation when necessary if the mold becomes too hot (above 450 F.) and may be further employed to discontinue the supply of current to the induction coil during the preheating operation when the temperature of the mold has been raised to about 430 F. This control apparatus is not shown.

It will be understood that the induction coil is used only for preheating and is maintained otherwise in its righthandmost position (Fig. l) as during casting operations. Desirably a shield (not shown) is provided to surroundthe mold during castin operations to catch any metal thrown off by the mold. A chute E30 (Figs. 1 and 2) is also provided below the mold to receive newly cast balls from the mold and to carry them away.

There are many features of the apparatus of this invention which are critical because of the nature of the metal being cast. Thus fine temperature control as well as proper metal handling is required if desirable, dense, smooth, dross-free and non-porous castings are to be obtained. Aside from the criticality of the temperature of the mold as above discussed, it should be pointed out that the molten metal must be introduced very quickly into the mold if prop-er castings are to be obtained. With one particular casting apparatus constructed in accordance with this invention, it has been found that the entire charge of molten metal must be introduced into the mold within from four to six seconds. If this period of time is longer, the castings formed are apt to be undesirably rough.

In the aforementioned particular casting apparatus, the following are specific characteristics. The mold halves are made of Mehanite, a particular form of cast iron, and together weigh about 430 pounds. Each mold half is provided with 36 hemispherical cavities by which 36 ball castings may be formed in one casting operation, their total weight being approximately .6 pounds. About 20 additional pounds of molten metal are supplied to the mold to form the sprue whose purpose is to keep the mold full during the cooling and solidifying period and to absorb the shrinkage effects of cooling. As stated above, it has been found that the 66 pounds of molten metal must be supplied to the mold in about 4 to 6 seconds to obtain desirable castings. In addition, it has been found that in this particular apparatus the molds must be rotated at such a speed that the centers of the mold cavities have a lincar speed of about 75 feet per second. If the speed is lower, the successive increments of metal entering the cavities are too large and one increment may solidify before the next is added. Thus an undesirable, Stratified ball, which is not solid, may result. From this it will also be clear that the rate of rotation of the mold must be sufiiciently great to give the previously set forth linear speed prior to admission of any molten metal into the mold.

In this specific apparatus it has been found that force -duringscasting;.. The resulting-force between the. moldi'ihalvesx when: the: aforementionecb oil pressure. employed. is equal; to about: 121/ tons.

Thelspecificinducti'on heater? of? the aforementiioned specific .apparatusahas: a 141 turn coil: which withzwater cooiingzpermit'sathe application. thereto I of at least 600 amperes and I*l-5-.volt's, the current being a 60 cycle alternating one. This current will cause thecomposite moldto beheated to 400450?"F-.; in ayperiod of about40'minutes without raising the temperature of the surrounding parts, andiparticularly the thrust bearing,l.0,, of the apparatus substantially above 200 EJ.

It should be undrst'ood1however, thatbyreason ofour setting forth specific characteristics of a. specific, apparatus according-to our invention, our invention should not beli'mited thereby but rather it should be considered to. be as broad as are the appended claims. 1

Theoperat'ion of the apparatus of this invention maybe substantially fully automatic by providing certain controls which, are notlhere,-dis closed butwhich are conventional in themselves. To.- initiatecaSting with theapparatus, the mold halves must first be heatedto-the above prescribed temperature and this may be accom plished by moving the mold halves into contact with each other and then moving the induction coil into position to surround them as illustrated in Fig. 2. As stated, about 40 minutes is required to bring the temperature of the molds up to 400 to 450 F. Yet during this preheating operation, the surrounding parts of the apparatus, and particularly the thrust bearing l8, are not heated to above 200. When the mold halves are at the proper temperature, the preheating operation is discontinued and the induction coil moved to the position illustrated in Fig. l. The motor M is then energized and sufficient time permitted to elapse to permit the mold to be brought up to the proper rotationa1 speed. Molten metal is then admitted to the mold through the stainless steel delivery pipe H5 and removable gooseneck I I6 in the manner set forth in our aforementioned application Ser. No. 251,024. All of the molten metal required for a single casting operation is discharged into the mold preferably in from 4 to 6 seconds. If desirable, and as above indicated, a carbon dioxide atmosphere may be maintained .within the mold to shield the molten metal discharged thereinto from air. An automatic timer, not shown, deenergizes the electric motor after the lapse of a predetermined period of time and the mold is brought to rest. Mold half I I is then retracted to the right as seen in Fig. 2 and the castings therein discharged into the carry-off chute I30. The mold halves may also be cleaned at this time and periodically may be sprayed with a special oil which breaks down with heat, leaving a carbon deposit thereon.

Successive batches of ball castings may be formed by repeating the above-described operation over and over again. It will be clear, however, that the mold preheating step of the operation need be performed only at the beginning of a series of operations after the apparatus has had a period of disuse and the mold permitted to become cool. Actually, during a series of operations the mold tends to become too hot by reason of the repeated batches of molten metal east therein. and" for: this reason, as; previously stated, cooling fans may be. employed. These fans'may be energized-a automatically whenever the: moldtemperature approaches a. predetermined maximum'value.

It willbe understood; that various changes and modifications may. be'made in the: apparatus described: above without departing from the scope of, ourinvention asset forth in, the appended claims.

We claim:.

1. In acentrifugal cadmium castingapparatus including a pair of'mold halves adapted when invface-t'o-face contact with each other to form a mold; thefaceof eachmold half containing a plurality ofcircumferentially spaced hemispherical cavities, means contained .on the opposing faces ofthe mold halves for rotationally positioning the mold halves with respect to each other so that the rimsofthe-cavities in one mold face will. coincidewith the rims of the cavities in the other. mold 'facewhen the mold faces abut each. other, a horizontal hollow shaft for supporting one mold half and providing access to the entrance of. the moldlfor molten metal delivery means, a thrust bearing supporting said hollow shaft and mold half for rotation about the 1ongitudinal axis of said shaft and mold but preventing substantial movement of the shaft or 'moldhalf 'long-it'udihall y'of said axis, a horizontal drive shaft supporting the other mold half, the longitudinal axes of the mold halves and shafts being aligned and the mold halves facing each other, at least one bearing supporting said drive shaft and permitting both rotational and longitudinal movement thereof, means for rotating said drive shaft, means for moving said drive shaft longitudinally to urge said other mold half supported by the drive shaft into face-toface contact with the mold half supported by the hollow shaft, said means also being adapted to move the drive shaft in an opposite direction to separate the mold halves, and means for preheating and maintaining the mold halves within a predetermined temperature range when said mold halves are in said face-to-face contact, the combination therewith of a plurality of channels in the face of each mold half, each of said channels leading radially from a common central cavity to a hemispherical cavity, each channel having side walls which diverge slightly toward its corresponding hemispherical cavity and each channel being provided with a sharp ridge spaced a short distance from its point of juncture with said cavity.

2. An improved centrifugal cadmium casting apparatus according to claim 1 in which the heating means for preheating the mold halves prior to a casting operation comprises a number of turns of copper tubing, and which includes means movably mounting said copper tubing to surround said mold halves in any position of rotation thereof when the latter are in face-to-face contact and for movement to a position completely out of the plane of rotation of the mold halves when in face-to-face contact, whereby When a charge of molten cadmium is contained in the composite molds and the latter is rotated the heating means will lie out of the path of travel of any flying metal.

3. An improved centrifugal cadmium casting apparatus according to claim 1 in which the means for moving the horizontal drive shaft longitudinally comprises an annular cylinder surrounding a portion of said drive shaft, an annular piston mounted in said cylinder, expanding piston rings mounted in and completely encircling the outer peripheral face of said annular piston, contracting piston rings mounted in and completely encircling the inner face of said piston adjacent the inner wall of said annular cylinder, a thrust bearing supported on said drive shaft between said annular cylinder and the mold half supporting end of said drive shaft, a plurality of connecting rods connecting said annular piston to said thrust bearing, a fluid conduit connected to one end of said annular cylinder and adapted to supply fluid under pressure thereto, and a fluid conduit connected to the opposite end of said annular cylinder and adapted to supply fluid under pressure to said opposite end of said cylinder.

4. An improved centrifugal cadmium casting apparatus according to claim 3 in which the drive shaft is provided with a rearwardly facing shoulder between said thrust bearing and said mold half and in which said thrust bearing comprises a ring collar secured to said drive shaft but spaced from said shoulder, a plurality of roller bearings surrounding said drive shaft between said shoulder and. said collar and extending radially from said drive shaft, said roller bearings being flanked on either side by a bearing race, and a non-rotatable ring member surrounding said roller bearings, said bearing races, and said collar.

5. An improved centrifugal cadmium casting apparatus according to claim 3 in which each contracting piston ring comprises a plurality of arcuate segments assembled in the form of a ring with adjacent ends of each adjoining pair of segments spaced from one another, and spring means surrounding said segments and urging them into contact with each other to form an uninterrupted ring.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,693,283 Mix Nov. 27, 1928 1,698,624 Dale Jan. 8, 1929 1,908,607 Hokin May 9, 1933 1,939,623 Clamer Dec. 12, 1933 2,000,155 White May 7, 1935 2,172,798 Littmann Sept. 12, 1939 2,277,334 Le Tourneau Mar. 24, 1942 2,359,524 Lane Oct. 3, 1944 2,479,610 Frei Aug. 23, 1949 2,486,388 Brinton Nov. 1, 1949 2,517,317 Janco Aug. 1, 1950 2,536,692 Miller Jan. 2, 1951 2,557,971 Jacklin June 26, 1951 2,637,079 Kemppe May 5, 1953 

